BACKGROUND: Ultrasound is a well-validated adjunct to central venous cannulation; however, previous reviews of ultrasound-guided radial artery cannulation have been inconclusive. The aim of this study was to assess the use of ultrasound in radial artery cannulation in adult and paediatric populations. METHODS: A systematic search of five major databases for all relevant articles published until November 2015 was conducted. Randomized controlled trials of radial artery cannulation with and without ultrasound guidance were included...